Volume 14, No. 2, March 2014, Pages 572-584 PDF(3.52 MB)
Preparation and Characterization of Lanthanum-Promoted Copper-based Oxygen Carriers for Chemical Looping Combustion Process
Yan Cao1, Song P. Sit2, Wei-Ping Pan1
1 Institute for Combustion Science and Environmental Technology (ICSET), Department of Chemistry, Western Kentucky University, Bowling Green, KY 42101, USA
2 Cenovus FCCL Ltd, Canada
Chemical looping combustion (CLC) is an oxygen combustion process that results in the higher CO2 concentrations in flue gases. Copper-based oxygen carriers have high reactivity, resulting in high purity CO2 generation, but face the challenges of low copper melting point and potential thermal sintering under high-temperature cyclic operation. A temperature-programmed reduction and oxidation (TPR-TPO) technique (Redox) was used to simulate of the cyclic operation of copper-based oxygen carriers in the CLC process. Multiple material characterization methods were applied to the fresh and used oxygen carriers, including the determination of pore structure and surface area by Brunauer-Emmett-Telle (BET), crystal structure by X-ray diffraction (XRD) and surface phase diagram analysis by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX). Thermally stable copper-based oxygen carriers have been successfully prepared using commercially-available Al2O3 as the supporting material and selected additives. A substantial resistance to agglomeration and durability in over 50 cyclic Redox tests under high temperature conditions (oxidation at 800°C and reduction at 800°C) has been confirmed for the Sample labeled as CLCA. The oxygen transfer capability was almost stable, and the CuO content ranged from 20 wt% to 23 wt% for the CLCA sample. The supporting material (Al2O3) significantly impacted the oxygen releasing performance and thermal stability of the copper-based oxygen carriers, due to the formation of a new crystal phase (CuAl2O4) which cross-links the CuO and the γ-Al2O3. Lanthanum accelerated the cross-linking between CuO and Al2O3.
Chemical looping combustion; Oxygen carriers; Copper; Additives.